This invention relates in general to universal joint assemblies for use in vehicular drive train and steering systems. In particular, this invention relates to a universal joint assembly including a cross having at least one trunnion that rotatably supports a bearing cup on the end thereof, wherein a bearing insert formed from a ceramic or composite material is disposed between the trunnion and the bearing cup.
Universal joints are well known devices that provide a driving connection between two members adapted to rotate about non-aligned axes of rotation. Universal joints are widely used, for example, to connect rotatable members in vehicle drive train systems and in vehicle steering shaft systems. In a typical drive train system, a first universal joint is connected between an output shaft of an engine/transmission assembly and a first end of a driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and an input shaft of an axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
A typical structure for a universal joint includes a cross having a central body portion with four cylindrical trunnions extending outwardly therefrom. The trunnions are oriented in a single plane and extend at right angles relative to one another. A hollow cylindrical bearing cup is mounted on the end of each of the trunnions. Needle bearings or similar means are provided between the outer cylindrical surfaces of the trunnions and the inner cylindrical surfaces of the bearing cups to permit relative rotational movement between the trunnions and the bearing cups. The bearing cups mounted on a first opposed pair of the trunnions are connected to a first yoke that, in turn, is secured to one of the rotatable components of the vehicle drive train system. Similarly, the bearing cups mounted on a second opposed pair of the trunnions are connected to a second yoke that, in turn, is secured to a second one of the rotatable components of the vehicle drive train system.
One problem that is associated with the use of traditional universal joints is friction. Friction occurs between the trunnions of the cross and the bearing cups mounted thereon when the such components move relative to one another as the universal joint is rotated at an angle during use. The amount of such relative movement is dependent upon the speed of such rotation and the magnitude of the angular misalignment between the two shafts that are connected together by the universal joint. As mentioned above, a plurality of needle bearings or other bearing structures have traditionally provided between the trunnion of the cross and the associated bearing cup to reduce the amount of friction therebetween and, therefore, the amount of heat and wear that occurs as a result of such friction. As a precaution in dealing with the heat generated by the rapid rotation of the universal joint, it is known to subject portions of some or all of the trunnions, the roller bearings, and the bearing cups to a heat treating process for greater hardness to withstand the rigors of high temperature operation caused by friction. Additionally, lubricant is often provided in the region of the needle bearings between the bearing cups and the trunnions in the universal joint to reduce the amount of friction generated during use.
Although known universal joints have functioned satisfactorily, it would be desirable to provide an improved structure for a universal joint that contains components that generate less friction during operation than is produced by conventional universal joints and that are more capable of handling the heat that is generated during use. It would also be desirable to provide such an improved universal joint that contains a lesser number of parts and, therefore, is lower in cost to manufacture and assemble than typical universal joints.
This invention relates to a universal joint including a cross member having a plurality of trunnions extending outwardly therefrom. A hollow bearing cup is disposed about the end of each of the trunnions. Each of the bearing cups has an open end, a closed end, and an inner surface that is disposed about a bearing surface formed on the trunnion. An insert is disposed between the bearing surface of the trunnion and the inner surface of the bearing cup provided thereon. In a first embodiment, an annular groove is formed in the inner surface of the bearing cup that receives the insert therein. In a second embodiment, the insert is disposed between the cylindrical bearing surface of the trunnion and the cylindrical inner surface of the bearing cup. The insert is formed from either a ceramic material or a composite material. The bearing cup may be formed from a metallic material that is molded about the insert.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.